1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting a liquid such as an ink.
2. Description of the Related Art
Requests for the enhancement of a recording speed and an image quality of an ink jet printer have progressively increased, and resulting liquid ejection heads tend to have a higher density and an elongated size. As a dot density of the liquid ejection head is enhanced from a conventional 600 dpi to 1,200 dpi, a sectional area of a flow channel wall which constitutes a flow channel of an ink tends to decrease and a mechanical strength of an ejection orifice forming member tends to be lowered. For this reason, it is notably concerned that the ejection orifice forming member tends to be easily deformed by stress. In addition, rigidity against the stress is relatively lowered in a central part in an array direction of a plurality of ejection orifices, in which the volume of the ejection orifice forming member is small, compared to that in both ends in the array direction of the ejection orifices. For this reason, as the liquid ejection head is elongated, the central part in the array direction of the ejection orifices becomes easily affected by the stress, and there is concern that the ejection orifice forming member is deformed. In the case where the deformation has occurred in the ejection orifice forming member, the ejection orifice is deformed, and it becomes difficult for a droplet to be stably landed at a desired position through the ejection orifice. As a result, the record quality of a recorded article results in being lowered.
As a measure of suppressing such a deformation of the ejection orifice forming member, Japanese Patent Application Laid-Open No. 2000-158657 discloses a configuration in which a beam-like projection is provided in the ejection orifice forming member at a position which faces an ink supply orifice, thereby enhancing the rigidity of the ejection orifice forming member. When the rigidity of the ejection orifice forming member is enhanced, an effect of suppressing the deformations of the ejection orifice forming member and the ejection orifice is obtained.
In addition, Japanese Patent Application Laid-Open No. 2007-283501 discloses a configuration in which a reinforcing rib that extends from the beam-like projection toward the ejection orifice and comes in contact with the substrate is formed integrally with the beam-like projection, thereby enhancing the rigidity against an external force and suppressing the deformations of the ejection orifice forming member and the ejection orifice.
However, the configuration disclosed in Japanese Patent Application Laid-Open No. 2000-158657 has the following problem. In the central part in the array direction of the ejection orifices in the ejection orifice forming member, a volume occupied by the ejection orifice forming member is relatively small compared to that in both the ends, and it is concerned that the central part tends to be easily deformed. This concern much more remarkably appears as the ejection orifice forming member is elongated. This is because when the beam-like projection is provided in the ejection orifice forming member, the rigidity is uniformly enhanced in the whole ejection orifice forming member, and accordingly it is still concerned to originate in a difference of the rigidity between both ends and the central part in the array direction of the ejection orifices.
In addition, when the volume of the beam-like projection is sufficiently increased so as not to cause the deformation of the ejection orifice forming member, a position onto which the stress acts results in moving to a portion at which the rigidity is relatively low, in other words, to an interface between the substrate and the ejection orifice forming member. As a result, it is concerned that the ejection orifice forming member is separated from the substrate. Accordingly, it is difficult to solve a problem that the record quality of the recorded article is lowered.
In addition, the configuration disclosed in Japanese Patent Application Laid-Open No. 2007-283501 has the following problem. Even in the structure having a reinforcing rib, the ejection orifice forming member still has a smaller volume in the central part in the array direction of the ejection orifices compared to that in both the ends in the array direction, and tends to easily cause the deformation in the central part. This tendency much more remarkably appears as the ejection orifice forming member is elongated. The configuration disclosed in Japanese Patent Application Laid-Open No. 2007-283501 cannot resolve such a tendency that the central part in the array direction of the ejection orifices tends to be easily deformed, which much more remarkably appears as the length of the ejection orifice forming member increases.